Refactor main window sizer setup and doc type UI logic in GUI class

Improve image mode handling and centering; update UI doc type logic

Ensure image mode is RGBA and use RGBA for compositing in render.py

Fix rendering PNG to DOC file

fix missing imports for font resolver

Clarify text image sizes and background image scaling details in README

Add PSPDOC decryption and extract doc_size_flag from data

Update extraction info

Add new keys and reorder entries in KEY_VAULT dictionary

- More fixes...